/**
  * Retrieve HTML classes for a field container.
  *
  * @since 4.1.0
  *
  * @param string $id Field id.
  * @return string
  */
 protected function siw_field_class($id)
 {
     $classes = array('simple-image-widget-field', 'simple-image-widget-field-' . sanitize_html_class($id));
     $hidden_fields = Simple_Image_Widget_Plugin::get_hidden_fields();
     if (in_array($id, $hidden_fields)) {
         $classes[] = 'is-hidden';
     }
     return implode(' ', $classes);
 }
 /**
  *
  */
 public function test_image_size_names()
 {
     $sizes = Simple_Image_Widget_Plugin::get_image_size_names();
     $this->assertEquals(4, count($sizes));
     $this->assertEquals('Thumbnail', $sizes['thumbnail']);
 }